Subnet planning tools before you touch the network.
Use this path to decode an address block, convert masks, split ranges, catch overlaps, and sanity-check capacity before changing routing, DHCP, VLANs, or firewall rules.
Educational planning utilities only — confirm production network changes against your actual router, firewall, cloud, ISP, and change-control requirements.
Decode first
Confirm the network, broadcast, usable range, and host count before editing DHCP, routing, or firewall rules.
Split carefully
Use the subnet splitter when you need equal child networks, the range-to-CIDR converter for irregular ranges, and the overlap checker before peering.
Plan capacity
Move to the network planner when VLANs, sites, gateways, and headroom all need to line up.
CIDR Subnet Calculator
Decode a CIDR block into subnet mask, wildcard mask, network, broadcast, usable range, and host count.
IP Address + Subnet Mask Calculator
Start from an IP and dotted-decimal mask when that is what the device or ticket gives you.
Subnet Mask to CIDR Converter
Convert prefixes, masks, wildcard masks, and host counts without memorizing the table.
Subnet Splitter Calculator
Split a parent CIDR into smaller equal-size networks before assigning ranges.
IPv4 Range to CIDR Converter
Summarize a start/end range into the smallest set of CIDR blocks.
IP Overlap / VPN Range Checker
Check LAN, VPN, cloud/VPC, partner, and site ranges for overlaps before peering or routing.
Network Planner
Use once the subnet math needs to become a site, zone, VLAN, gateway, and growth plan.
Before applying changes
These tools are for planning and conversion. Confirm production changes against router, firewall, cloud, ISP, DHCP, and documentation requirements before applying them.
This collection page does not accept or store network inputs. Links are plain local paths with no query strings.